Dual backflow check valve

ABSTRACT

A dual backflow check valve for use in a vacuum sewage system, wherein the check valve includes a valve body and a valve flap pivotally mounted inside the valve body, the valve body having a primary (branch) conduit and a secondary (service) conduit entering the primary conduit at an acute angle. The primary conduit has an upstream portion forming a primary inlet into the valve body and a downstream portion forming a primary outlet out of the valve body, and the secondary conduit forms a secondary inlet into the valve body. The valve flap is pivotable between two positions, a first position in which it prevents fluid from entering the secondary conduit and a second position in which it prevents fluid from entering the upstream portion of the primary conduit. Preferably, the primary conduit and the secondary conduit of the check valve are oriented in a substantially horizontal plane in the vacuum sewage system.

This application claims the benefit of U.S. Provisional ApplicationSerial No. 60/068,130, filed Dec. 19, 1997.

FIELD OF THE INVENTION

This invention relates to a wye-shaped dual backflow check valve for avacuum sewage system and a vacuum sewage system incorporating thewye-shaped dual backflow check valve.

BACKGROUND OF THE INVENTION

Check valves are often used in plumbing and piping systems to block theflow of fluid in a particular direction. Specifically, backflow checkvalves are designed for installation in a sewer pipe to allow sewage topass downstream through the main line while preventing water and sewergases from traveling upstream into another line, i.e. to preventbackflow or backsurge. Backflow check valves have been used in vacuumsewage systems such as the sewage systems disclosed in U.S. Pat. No.4,373,838. Typically, check valves in known vacuum sewage systems areinstalled entirely in the service lines which feed into a branchline(s). These service lines generally flow upwardly to branch lines inthe vacuum system, so check valves are installed in the service lines toprevent back surge into the service line. However, check valves arerestricted in use in these systems because they frequently requiremaintenance. While the prior art check valves prevent backflow into theservice line, backflow into the branch line is not prevented when fluidflows downstream from the service line. As a result of this problem,backflow or back surge of up to 20% of the transported fluids has beenobserved in the branch line. This is a significant problem because aline that becomes filled with liquid in a vacuum sewage system may failto operate due to excessive pressure loss (i.e., may become“waterlogged”).

The present invention relates to a wye-shaped check valve installed in avacuum sewage system, wherein the check valve prevents backflow ofsewage into the service line and the branch line. This is significant inthat it not only prevents the possibility of filling a service line or abranch line with liquid, but also increases the operating efficiency ofthe system because all relevant force is applied in the proper directionof flow. Thus, sewage will be conveyed a further distance towards adisposal station with one valve (evacuation) cycle. In addition to theabove-described advantages, the wye-shaped dual check valve of thepresent invention permits vacuum system service lines to be connected tobranch lines in substantially the same horizontal plane. This provides asignificant advantage because better overall drainage efficiency of thesystem is obtained by incorporating as few profile changes in the sewagetransport lines as possible, thus allowing the fluid flow to experienceas few dynamic flow changes as possible.

SUMMARY OF THE INVENTION

These and other problems are eliminated by the present invention whichprovides for a wye-shaped dual backflow check valve in a vacuum sewagesystem.

In one embodiment of the present invention, the dual backflow checkvalve used in a vacuum sewage system has a valve body including aprimary (branch) conduit with an upstream and a downstream portion and asecondary (service) conduit; and a valve flap hinged at the junctionbetween the primary conduit and the secondary conduit such that thevalve flap can prevent flow into the upstream portion of the primaryconduit or into the secondary conduit. In another embodiment of thepresent invention, the upstream portion of the primary conduit forms aprimary valve seat and the secondary conduit forms a secondary valveseat, wherein the valve flap can sealingly engage either the upstreamportion of the primary conduit or the secondary conduit. Yet anotherembodiment of the present invention includes a rubber gasket on both theprimary valve seat and the secondary valve seat. In another embodimentof the present invention, the primary conduit and the secondary conduitare oriented on a substantially horizontal plane. In still anotherembodiment of the present invention, the primary valve seat and thesecondary valve seat are slightly angled in a direction from the valveflap hinge and toward the downstream portion of the primary conduit. Inanother embodiment, the upstream portion of the primary conduit and thesecondary conduit form an acute angle of approximately forty fivedegrees.

It is therefore a primary object of the present invention to provide adual backflow check valve used in a vacuum sewage system wherein thedual check valve can prevent backflow into either the primary (branch)line or the secondary (service) line of the vacuum sewage system.

Another important object of the present invention is to provide a dualbackflow check valve which operates efficiently when both the primaryconduit and the secondary conduit are oriented on a substantiallyhorizontal plane.

It is also an important object of the present invention to provide adual backflow check valve which allows the primary (branch) line of thedrainage system to be buried at a shallower depth than necessary withthe prior art, thereby significantly decreasing the costs associatedwith designing and installing a drainage system.

Another object of the present invention is to provide a dual backflowcheck valve which includes fewer profile changes than the prior art,thus allowing the design of a drainage system of greater efficiencybecause of increased rates of fluid flow and/or decreased probability of“waterlogging” (i.e., excessive pressure loss).

Additional objects and advantages of the present invention will becomeapparent and a more thorough and comprehensive understanding may be hadfrom the following description taken in conjunction with theaccompanying drawings forming a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a vacuum sewage system including a dualbackflow check valve embodying the present invention;

FIG. 2 is a cross-sectional view of a dual backflow check valveembodying the present invention;

FIG. 3 is a top view of a valve flap, tab, and hinge pin used in thecheck valve of FIG. 2;

FIG. 4 is an exploded perspective view of a dual backflow check valveembodying the present invention;

FIG. 5 is a perspective view of a dual backflow check valve embodyingthe present invention, wherein the primary conduit and the secondaryconduit are separate components that are screwed together;

FIG. 6 is a cross-sectional view depicting fluid flow from the secondaryconduit of the check valve of FIG. 2;

FIG. 7 is a cross-sectional view depicting fluid flow from the upstreamportion of the primary conduit of the check valve of FIG. 2; and

FIG. 8 is a perspective view of the service conduit of the dual backflowcheck valve of FIG. 4.

DETAILED DESCRIPTION

The vacuum sewage system 10 of the present invention, as illustrated inFIG. 1, includes a service line 12 having a substantially verticaldischarge pipe portion 14 and a substantially horizontal pipe portion16. In fluid communication with and downstream from the verticaldischarge pipe is a first sewage holding tank 18. Operably associatedwith the sewage holding tank 18 is a valve unit 20 and a valve actuator22 which senses when the sewage level in a holding tank has reached adesired discharge level. This portion of the system is described indetail in U.S. Pat. No. 4,373,838, which is hereby incorporated byreference. When the sewage level in the holding tank 18 reaches thedischarge level, the actuator 22 opens the valve 20. Because thepressure on the downstream side of the valve 20 is low (i.e, undervacuum) and the holding tank is maintained at about atmosphericpressure, the opening of the valve 20 results in the evacuation ofsewage from the holding tank and through the vertical discharge pipe 14.The sewage then travels through the horizontal portion 16 of the serviceline. Next, the sewage flows to a branch line 26 through the wye-shapeddual backflow check valve 100 which connects the service line 12 to thebranch line 26. After passing through the wye check valve 100, sewageflows through the downstream portion 30 of the branch line to a mainvacuum line 32. Although not shown, several service lines may beconnected to the branch line with a corresponding wye check valve 100located at the juncture between each service line and the branch line.In this manner, sewage from each of the service lines will betransported through a corresponding wye check valve and into the branchline. Another possibility not shown is to locate a wye check valve 100between the downstream portion 30 of the branch line and the main vacuumline 32.

As shown in FIG. 2, the wye check valve 100 of the present invention hasa valve body 102 comprising a primary (branch) conduit 104 and asecondary (service) conduit 106. Primary conduit 104 has an upstreamportion 108 and a downstream portion 110 being aligned in such a mannerthat both portions 108 and 110 have substantially the same longitudinalaxis. To transport fluid through valve body 102, the secondary conduit106 forms a secondary (service) inlet 118 into valve body 102, theupstream portion 108 of primary conduit 104 forms a primary (branch)inlet 120 into valve body 102, and the downstream portion 110 of primaryconduit 104 forms a primary (branch) outlet 121 out of valve body 102.In the preferred embodiment, each of secondary inlet 118, primary inlet120, and primary outlet 121 are generally elliptical in shape.

As shown in FIG. 2, at the approximate midpoint of the upstream portion108 of primary conduit 104, bottom wall 112 inclines upwardly. Thisupward incline allows the upstream portion 108 of the primary conduit totransition to the downstream portion 110 at inclined surface 113. Theinclined surface 113 defines a primary (branch) valve seat 114 whichencircles primary inlet 120. Valve flap 116 is seated on primary valveseat 114 when sewage is flowing through secondary conduit 106. In apreferred embodiment, encircling secondary inlet 118 is a secondary(service) valve seat 115 for seating valve flap 116 when sewage isflowing from the upstream portion 108 of primary conduit 104.

As shown in FIG. 2, the secondary or service conduit 106 joins theprimary conduit 104 at a location between upstream portion 108 anddownstream portion 110 and forms an acute angle with the upstreamportion 108 of the primary conduit. Preferably, this angle is about 45°.

Referring to FIGS. 2-5, the internal construction of the wye check valve100 shall be further described. Pivotally secured within valve body 102adjacent secondary inlet 118 and primary inlet 120 is valve flap 116.Valve flap 116 is generally elliptical in shape to match the generalshapes of primary valve seat 114 and secondary valve seat 115. Valveflap 116 may also include a raised seal portion 117 about its peripheryto provide a better seal against primary valve seat 114. A hinge recess128 is provided at an area between secondary inlet 118 and primary inlet120. To pivotally secure valve flap 116 to the valve body, a hinge pin126 is secured in hinge recess 128. A tab 122 extends from valve flap116 and has a looped portion which forms a cylindrical hole 124 throughwhich hinge pin 126 is rotatably inserted. Valve flap 116 and tab 122are constructed such that the combination of the two provides asubstantially rigid structure. This is particularly important in thevacuum sewage system of the present invention due to the high velocityof the sewage (10-30 feet per second) traveling through the check valve.In the preferred embodiment shown in FIGS. 2 and 3, valve flap 116 iscomposed of EPDM rubber and tab 122 is constructed of stainless steeland extends within flap 116 to reinforce the valve flap.

Valve body 102 may be constructed of any suitable materials known in theart. Preferably, the valve body is constructed of a glass-filledpolypropylene material. Further, the valve body can be composed of asingle unit. However, in the preferred embodiment shown in FIGS. 2 and4-5, the secondary service conduit 106 and primary conduit 104 areseparate unitary components that are secured to each other to form valvebody 102. In this embodiment, secondary service conduit 106 comprises aunitary service component that includes secondary inlet 118 and primaryconduit 104 comprises a unitary service component that includes primaryinlet 120 and primary outlet 121. These separate unitary components arefastened together with screws 130 disposed through screw holes 132 and134 in the primary conduit 104 and secondary service conduit 106,respectively. The angle of entry of fluid through secondary inlet 118into primary conduit 104 can be varied by choosing a secondary conduit106 from a group having secondary inlets oriented at differing angles.Additionally, a rubber gasket or seal 136 (FIG. 4) disposed between thecomponents provides a fluid-tight seal between the conduits when theyare screwed together.

The operation of the wye check valve 10 is illustrated in FIGS. 6 and 7.In FIG. 6 there is shown the operation of the wye valve when flow isentering through the secondary (service) conduit and into the downstreamportion of the branch line toward the main vacuum line. As shown, theflow of sewage through the secondary conduit holds the flap down againstthe primary valve seat so that no or little flow is allowed to enter theupstream portion of the branch line (see FIG. 1). FIG. 7 shows the wyecheck valve when flow is moving from the upstream portion to thedownstream portion of the branch line. As shown, the flow of sewagethrough the branch line lifts the valve flap against the service valveseat, allowing sewage to flow to the downstream portion of the branchline and into the main vacuum conduit but preventing flow from enteringthe service line.

While FIG. 1 shows the wye check valve positioned with the secondary(service) conduit extending upwardly to receive the service line, in apreferred embodiment of the vacuum sewage system the secondary serviceconduit is oriented substantially horizontally and is substantially onthe same plane as the branch line. Several advantages are achieved bysuch a horizontal orientation of the wye check valve. For example, byorienting the wye check valve on substantially the same horizontal planeas the branch line one eliminates a profile change in the system,thereby improving the efficiency of the system. In other words, ahorizontal orientation allows the use of less energy in the vacuumsystem because the fluid flow does not experience as many changes inelevation. Another advantage of the above-described horizontalorientation of the wye check valve is that it allows the branch line andthe main vacuum line to be buried at shallower depths, therebydecreasing the costs associated with designing and installing a vacuumdrainage system.

Other alternative embodiments of the wye valve and sewage systemdisclosed herein are considered to be part of the present invention. Onesuch alternative embodiment relates to the angle of inclination of theprimary valve seat 114 shown in FIG. 2. In particular, primary conduitvalve seat 114 is shown to be oriented such that it extends from aposition adjacent hinge pin 126 and hinge pin recess 128 and anglestoward the downstream portion 110 of primary conduit 104. Angling thevalve seat in this manner helps to minimize the profile change necessaryas fluid flows downstream from the secondary conduit, thus furtherminimizing loss of fluid pressure and increasing efficiency. Similarly,secondary valve seat 115 is also angled toward the downstream portion110 of primary conduit 104. As shown in FIG. 8, a preferred embodimentincludes two seating pegs 140 located within secondary conduit 106 andextending front secondary (service) valve seat 115 in a manner thatprevents valve flap 116 from fully sealing with the secondary (service)valve seat 115.

Having thus described in detail a preferred selection of embodiments ofthe present invention, it is to be appreciated and will be apparent tothose skilled in the art that many physical changes could be made in theapparatus without altering the inventive concepts and principlesembodied therein.

What is claimed is:
 1. A vacuum sewage system comprising: a downstreamvacuum source for creating a pressure vacuum in said vacuum sewagesystem; and at least one dual backflow check valve apparatus, said dualbackflow check valve apparatus comprising: a valve body attached to saiddownstream vacuum source, said valve body defining a branch conduithaving an upstream portion and a downstream portion, and a serviceconduit extending from said branch conduit from a location between theupstream portion and the downstream portion of said branch conduit andforming an acute angle with the upstream portion of said branch conduit,said branch conduit and said service conduit each having an internalbore, the internal bores of said branch conduit and said service conduitbeing in fluid communication and forming a service inlet; a branch valveseat encircling the upstream portion of said branch conduit; a servicevalve seat encircling said service inlet formed between the internalbores of said service conduit and said branch conduit; and a valve flappivotally mounted inside said valve body, said valve flap having a firstposition wherein said valve flap seatingly engages said service valveseat and having a second position wherein said valve flap seatinglyengages said branch valve seat; wherein said valve flap pivots to saidfirst position and prevents backflow into said service conduit whenfluid flows from the upstream portion of said branch conduit to thedownstream portion of said branch conduit, and said valve flap pivots tosaid second position and prevents backflow into the upstream portion ofsaid branch conduit when fluid flows from said service conduit to thedownstream portion of said branch conduit.
 2. The vacuum sewage systemas set forth in claim 1 wherein: said branch valve seat is formed insaid valve body by reducing the internal bore of the upstream portion ofsaid branch conduit to a diameter less than the internal bore of thedownstream portion of said branch conduit.
 3. The vacuum sewage systemas set forth in claim 1 wherein: said branch valve seat forms a planeextending at an angle from a point adjacent the pivot location of saidvalve flap toward the downstream portion of said branch conduit.
 4. Thevacuum sewage system as set forth in claim 1 wherein said valve flapcomprises: a valve flap body having a substantially elliptical shape;and a tab having a secured end inserted into said valve flap body and ahinged end extending from said valve flap body.
 5. The vacuum sewagesystem as set forth in claim 4 wherein: said valve flap body has aperipheral edge, said peripheral edge having a raised seal portion. 6.The vacuum sewage system as set forth in claim 1 wherein: said valveflap is pivoted from said first position to said second position andfrom said second position to said first position by a pressure vacuumapplied by said downstream vacuum source to the downstream portion ofsaid branch conduit and by a force created by fluid flow toward thedownstream portion of said branch conduit.
 7. The vacuum sewage systemas set forth in claim 6 wherein: the upstream portion of said branchconduit has a longitudinal axis and the downstream portion of saidbranch conduit has a longitudinal axis; and the longitudinal axes of theupstream portion and the downstream portion of said branch conduit aresubstantially aligned.
 8. The vacuum sewage system as set forth in claim7 wherein: said branch conduit and said service conduit are oriented ona substantially horizontal plane.
 9. The vacuum sewage system as setforth in claim 7 wherein: said valve body has an interior contourbetween the upstream portion of said branch conduit and the downstreamportion of said branch conduit; said valve flap has a peripheral edge,said peripheral edge defining a curved path as said valve flap travelsbetween said first position and said second position; and the interiorcontour of said valve body substantially conforms to said curved pathdefined by the peripheral edge of said valve flap.
 10. The vacuum sewagesystem as set forth in claim 7 wherein: at least one-seating peg extendsfrom said service valve seat, said at least one seating peg preventingsaid valve flap from fully sealing said service valve seat while in saidfirst position.
 11. The vacuum sewage system as set forth in claim 7wherein: said acute angle formed between said service conduit and theupstream portion of said branch conduit is about 45 degrees.
 12. Thevacuum sewage system as set forth in claim 7 wherein: the serviceconduit and the branch conduit of said valve body are separable modularcomponents secured together with a fluid-tight seal.
 13. The vacuumsewage system as set forth in claim 12 wherein: said service conduitmodular component is selected from a plurality of service conduitmodular components having varying service conduit angles such that saidacute angle formed between said service conduit and the upstream portionof said branch conduit is dependent on the service conduit angle of saidselected service conduit modular component.
 14. The vacuum sewage systemas set forth in claim 12 wherein: said valve flap comprises a rubberflap body attached to a rotatable hinge, and said rotatable hinge isrotatably secured between said service conduit modular component andsaid branch conduit modular component.
 15. A vacuum sewage systemcomprising: a main conduit having an attached vacuum source for creatinga pressure vacuum in said vacuum sewage system; a branch conduit influid communication with said main conduit; at least one serviceconduit, said at least one service conduit being in fluid communicationwith said branch conduit; and at least one dual backflow check valve,said at least one dual backflow check valve being attached between saidbranch conduit and said at least one service conduit, said dual backflowcheck valve comprising: a branch inlet attached to an upstream portionof said branch conduit; a service inlet attached to said serviceconduit; a branch outlet attached to a downstream portion of said branchconduit; and a valve flap pivotally mounted between said branch inletand said service inlet, said valve flap having a first position whereinsaid valve flap blocks fluid backflow through said service inlet andhaving a second position wherein said valve flap blocks fluid backflowthrough said branch inlet.
 16. The vacuum sewage system as set forth inclaim 15 wherein: said valve flap is pivoted from said first position tosaid second position and from said second position to said firstposition by the pressure vacuum created by the attached vacuum source insaid main conduit and by a force created by fluid flow toward thedownstream portion of said branch conduit.
 17. The vacuum sewage systemas set forth in claim 15 wherein: the branch inlet and the branch outletof said dual backflow check valve comprise a unitary branch component;the service inlet of said dual backflow check valve comprises a unitaryservice component; and said unitary branch component and said unitaryservice component are secured together with a fluidtight seal.
 18. Thevacuum sewage system as set forth in claim 17 wherein: said unitaryservice component is selected from a plurality of unitary servicecomponents having service inlets oriented in varying angles, the serviceinlet of said selected unitary service component and the branch inlet ofsaid unitary branch component forming an angle dependent on the angle ofthe service inlet of said selected unitary service component.
 19. Thevacuum sewage system as set forth in claim 17 wherein: said valve flapcomprises a rubber flap body attached to a rotatable hinge, and saidrotatable hinge is rotatably secured between said unitary servicecomponent and said unitary branch component.
 20. The vacuum sewagesystem as set forth in claim 15 wherein: the upstream portion of saidbranch conduit has a longitudinal axis and the down stream portion ofsaid branch conduit has a longitudinal axis; and the longitudinal axesof the upstream portion and the downstream portion of said branchconduit are substantially aligned.
 21. The vacuum sewage system as setforth in claim 20 wherein: said branch conduit and said at least oneservice conduit are oriented on a substantially horizontal plane.
 22. Ina vacuum sewage system having a service conduit in fluid communicationwith a branch conduit, a method of preventing fluid backflow comprising:creating a vacuum in said vacuum sewage system; evacuating fluid throughsaid service conduit and said branch conduit, wherein fluid in saidservice conduit and fluid in an upstream portion of said branch conduitis evacuated to a downstream portion of said branch conduit, saidevacuation being driven by a pressure differential caused by saidvacuum; rotating a valve flap into a first position wherein said serviceconduit is sealed to prevent fluid backflow into said service conduit asfluid is evacuated from the upstream portion of said branch conduit tothe downstream portion of said branch conduit; and rotating said valveflap into a second position wherein the upstream portion of said branchconduit is sealed to prevent fluid backflow into the upstream portion ofsaid branch conduit as fluid is evacuated from said service conduit tothe downstream portion of said branch conduit.